The present invention relates to a combined moistening system for a printing machine, which can be universally used for water moistening and alcohol moistening.
In printing machines liquid distributing rollers are known which are rotated by friction with adjoining rollers to transfer a dampening agent from a reservoir containing such an agent to an impression or form roller of the printing machine.
One of the conventional moistening systems of the type under consideration can be converted from the water moistening to the alcohol moistening. Such a system is disclosed in DE-AS No. 1,929,624. Moisture in this conventional system is transmitted by a vibrating or oscillating roller which conveys the moistening liquid from the fountain roller to the impression roller through material-transferring distributing rollers. If an alcohol supplement is to be used at least one plain roller is interchanged whereby the material-transferring roller serves as a storing roller on the rubbing roller.
This conventional device, in which the oscillating roller is positioned between the fountain roller and the rubbing roller has the disadvantage because, due to the various velocities of the rubbing roller, which rotates with the machine speed, and of the fountain roller which takes on the dampening agent from the reservoir and rotates considerably slower, the oscillating roller, which is in contact either with the fountain roller or with the rubbing roller, would be subjected to acceleration or decelation. Oscillating shocks caused by the above acceleration and decceleration on the rollers of the known moistening system have a negative effect on the ink-moistening agent balance which should be quickly achieved in the printing machine because during the application of the oscillating roller to the rubbing roller or the fountain roller an uncontrolled slippage between those two rollers during the transmittal of the moistening agent can occur.
Another known moistening system has been described in the German patent publication DD-PS No. 100 435. This system can also be suitable for the alcohol supplement. A suitable displacement means can be utilized in that known system to provide for a continuous or interrupted roller contact between the rubbing roller, oscillating roller and the doctor roller. In this case the oscillating roller takes on the wetting agent directly from the fountain roller. The disadvantage of this otherwise satisfactory system is that the different velocities of the wetting agent-distributing rollers occuring during the transmittal of the wetting agent result in the uncontrollable moistening.